Method for making surface protective striking tools

ABSTRACT

An improved manufacturing process is provided for surface protective striking tools such as hammers and mallets. An elongate hollow core is fitted with impact heads at opposite ends thereof and filled with a flowable filler material such as small steel pellets prior to placement of the core into a mold cavity for injection mold formation of an outer encasement. During the molding step, the filler material provides a substantially rigid structural backstop which enables a core of lightweight construction to withstand typical injection molding parameters. The molded outer encasement ensheathes a skirt portion of the impact heads and any exposed portion of the core member to bind the impact heads to the core member. The molded outer encasement does not extend over an impact face of each impact head. A handle may also be molded with the outer encasement. A striking tool thus formed is removed from the mold, and some or all of the filler material is drained from the core through an open port. When a handle is provided, a reinforcing rod is inserted centrally within the handle so as to extend the length thereof. The rod may be heated prior to insertion into the handle to help secure the rod in place within the handle.

RELATED APPLICATIONS

This is a division of application Ser. No. 08/167,418, filed Dec. 14,1993, (U.S. Pat. No. 5,375,486) which is a continuation-in-part of U.S.patent application Ser. No. 08/006,127, filed Jan. 19, 1993, entitledCLOSED BACK SHOVEL AND METHOD 0F ASSEMBLY (U.S. Pat. No. 5,310,230),which is a continuation of U.S. patent application Ser. No. 07/757,670,filed Nov. 7, 1991 entitled CLOSED BACK SHOVEL AND METHOD 0F ASSEMBLY(abandoned), which is a continuation-in-part of U.S. patent applicationSer. No. 07/712,690, filed Jun. 10, 1991 and entitled PROCESS FORATTACHING TOOL HEADS TO ENDS OF COMPOSITE HANDLES (U.S. Pat. No.5,123,304).

BACKGROUND OF THE INVENTION

This invention relates generally to hand tools and related manufacturingprocesses. More particularly, the present invention relates to themanufacture of plastic molded surface protective striking tools, such ashammers and mallets, which permits tool components to be assembledtogether in a simplified manufacturing process, wherein the componentsare selected to maximize performance of the striking tool while loweringthe costs thereof.

Traditionally, surface protective striking tools, such as soft-facedhammers and mallets, have been manufactured much like other types ofstriking tools with the exception that the tool head or impact face ismade of a material intended to minimize damage to the work being struck.The tool or impact heads have often been made of rawhide, rubber,copper, brass, wood. The particular material chosen for the tool head orimpact face has been dependent upon the task to be accomplished.

In the course of time, improvements have been made to the design oftraditional surface protective striking tools. For example, surfaceprotective hammers have been devised which utilize a permanent ornon-sacrificial handle and head component, and interchangeable andreplaceable impact faces which are attachable to a holder provided inthe head of the permanent portion of the tool component. Suchinterchangeable or replaceable faces are made of a wide range ofmaterials, and particularly out of new engineering plastics, which oftenexhibit superior working characteristics, i.e., they are tougher,softer, more cut resistant, etc., than traditional tool heads forsurface protective striking tools. Such modern surface protective handtools which utilize a non-sacrificial holder and replaceable insertfaces have become very popular with professional mechanics and tradesmenbut, due to their comparatively high cost, such hand tools are not wellused by or known to the semi-professional or home mechanic.

Attempts have been made to design and manufacture tool components,including striking tools, in a more efficient manner while retaining thereliability, durability and performance of hand tools manufactured intraditional ways. Specifically, a variety of plastic encased toolcomponents are generally known in the art, wherein a skeletal coremember is contained within a resilient outer encasement or cladding ofmolded plastic material or the like. The tool component is produced byplacing the skeletal core member into a mold cavity which is then filledwith a selected thermoplastic molding compound under suitable conditionsof heat and pressure. The plastic material is permitted to cure,followed by removal of the plastic encased tool component from the moldcavity. Examples of such plastic encased tool components includeelongated tool handles, plastic-faced hammers and mallets, etc.

In the production of tool components of this general type, the skeletalcore member must have sufficient structural integrity to withstand thepressures and temperatures encountered in a typical injection moldingenvironment. That is, the core member must be able to retain itsstructural size and shape throughout the injection molding process, toprevent production of defective tool components. In the past, skeletalcore members of solid cross-section have been commonly used in themanufacture of plastic encased tool components. However, since the costof such tool components is primarily attributable to the cost ofmaterials, it is desirable to reduce or minimize the material used inthe skeletal core member to the extent possible without sacrificing therequisite strength. In this regard, reduction in the cross-sectionalsize of a solid core member is ineffective to reduce material costs,since additional molded plastic encasement material is required to formthe finished tool component.

Hollow skeletal core structures have been proposed for use in themanufacture of plastic encased tool components. A hollow memberbeneficially reduces the material cost in the finished tool componentwithout requiring the use of additional molded plastic encasementmaterial. Moreover, a hollow skeletal core reduces the weight of thefinished tool component, resulting in a lightweight tool product whichcan be especially desirable in certain applications. However, despitethe hollow construction of the skeletal core member, a substantialamount of core member material has still been required in order toprovide the core member with the necessary structural integrity towithstand injection molding processes.

There exists, therefore, a need for improvements in manufacturingprocesses for making plastic encased tool components, wherein a hollowcore member constructed from substantially minimum material quantitiesis contained within a resilient outer encasement of molded thermoplasticmaterial or the like. Additionally, there is a need for specialtystriking tools, such as surface protective hammers and mallets, whichare highly versatile in regard to the material utilized on the impactsurface, which retain the reliability, durability and performancecharacteristics of similar striking tools manufactured in traditionalways, and which have a substantially lower cost of manufacture than suchtraditional striking tools. Additionally, a need exists for suchstriking tools which may include a no-bounce feature, without materiallyincreasing costs. The present invention fulfills these needs andprovides further related advantages.

SUMMARY OF THE INVENTION

The present invention resides in improved surface protective strikingtools and related manufacturing processes. In one preferred form of theinvention, the striking tool comprises an elongate hollow core memberand a pair of impact heads each having an impact face and a skirtextending away from the impact face. The skirt of each impact head isfitted over a respective end of the hollow core member, and a moldedouter encasement ensheathes the skirts and any exposed portion of thecore member therebetween. The molded outer encasement binds the impactheads to the hollow core member leaving the impact faces exposed. Theskirt of each impact head includes surface irregularities to facilitateattachment of the molded outer encasement thereto. An access port isprovided through both the hollow core member and the molded outerencasement through which a flowable filler material may be added to orremoved from the hollow core member.

In another preferred form of the invention, a handle is formedintegrally with the molded outer encasement, which extends away from thehollow core member generally perpendicularly with respect to alongitudinal axis thereof. The access port extends generally centrallythrough the handle, and is plugged by a reinforcing rod disposed withinthe the handle. The reinforcing rod provides stiffness and strength tothe handle which might be unavailable if the most economical plasticmaterial were utilized for the molded outer encasement. The reinforcingrod includes an irregular outer surface which facilitates securing thereinforcing rod within the handle.

The present invention also concerns a manufacturing process for makingsuch surface protective striking tools. In accordance with the method, acore member is provided which defines a hollow interior space and anaccess port opening into the interior space. The interior space of thecore member is filled with a flowable filler material, and then theaccess port is closed to retain the filler material within the interiorspace. An impact head having an impact face a skirt extending awaytherefrom, is placed adjacent to one end of the core member such thatsaid one end of the core member is disposed within the skirt. The coremember with the filler material therein and the impact head thereon isplaced into a mold cavity, and then a plastic material is injected intothe mold cavity to form a resilient outer encasement on the core memberand the skirt of the impact head. The plastic material is allowed tocure to form the striking tool, after which the striking tool is removedfrom the mold cavity. The access port in the core member may then beopened to remove at least a portion of the filler material from theinterior space. The method of the present invention may further includethe step of forming a handle for the striking tool during the moldingstep.

The filler material typically comprises solid pellets having a diametricsize on the order of 0.005 inch. The method may include the step ofre-closing the access port after a limited portion of the fillermaterial has been removed from the core member to retain a residualportion of the filler material therein. This provides the resultantstriking tool with deadblow or nonrecoil characteristics.

When a handle is formed during the molding step, the step of re-closingthe access port includes the steps of inserting a reinforcing rod intothe handle so as to be disposed generally centrally therein andextending the length thereof. The reinforcing rod is provided withsurface irregularities, and is preferably heated prior to inserting itinto the handle such that upon insertion of the reinforcing rod, aninterior surface of the handle is softened and flows into contact withthe surface irregularities of the reinforcing rod to help secure itwithin the handle.

A second impact head having a second impact face and a second skirtextending away from the second impact face, may be placed adjacent to asecond end of the core member prior to the molding step. In this case,the molding step binds both impact heads to the core member.

Other features and advantages of the present invention will becomeapparent from the following more detailed description, taken inconjunction with the accompanying drawings which illustrate, by way ofexample, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a perspective view of a surface protective hammer manufacturedin accordance with the present invention;

FIG. 2 is a front elevational view, shown partially in vertical section,illustrating the step of filling an elongate hollow core member with aflowable filler material in accordance with the manufacturing process ofthe invention;

FIG. 3 is a front elevational view, shown partially in vertical section,illustrating the hollow core member having impact heads placed over eachend and placed within an injection mold, wherein a removable core pinextends away from the hollow core member generally perpendicularlyrelative to its longitudinal axis in alignment with that portion of themold for forming a handle, wherein the core pin effectively plugs anaccess port to the hollow core member;

FIG. 4 is a front elevational view, shown partially in vertical section,illustrating the assembled core member and impact heads of FIG. 3 withinthe injection mold, with a molded plastic outer encasement formedthereon;

FIG. 5 is a front elevational view, shown partially in vertical section,similar to FIG. 4, and illustrating removal of the core pin from thehandle, and removal of a portion of the filler material from the hollowcore member;

FIG. 6 is a front elevational view similar to FIG. 5, illustratinginsertion of a reinforcing rod generally centrally within the handlewhich, when inserted, closes the access port;

FIG. 7 is an enlarged, fragmented elevational section taken generally ofthe area indicated by the number 7 in FIG. 5, illustrating the manner inwhich the impact heads ensheathe a respective end of the hollow coremember, and further illustrating the manner in which the molded plasticouter encasement ensheathes a skirt portion of each impact head andadjacent portions of the hollow core member to secure the impact headsto the core member;

FIG. 8 is an enlarged fragmented elevational view taken generally of thearea indicated by the number 8 in FIG. 6, illustrating surfaceirregularities provided the reinforcing bar to facilitate securement ofthe reinforcing bar within the handle;

FIG. 9 is a perspective view similar to FIG. 1, illustrating anothertype of surface protective striking tool manufactured in accordance withthe present invention;

FIG. 10 is a front elevational view, shown partially in verticalsection, illustrating the elongate hollow core member having impactheads disposed at each end thereof, of the striking tool of FIG. 9,within an injection mold; and

FIG. 11 is a front elevational view, shown partially in verticalsection, of the striking tool of FIGS. 9 and 10, illustrating removal ofa portion of the filler material from the hollow core member after amolded plastic outer encasement is formed to secure the impact heads tothe core member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in the drawings for purposes of illustration, the presentinvention is concerned with the manufacture of surface protectivestriking tools. FIGS. 1-8 illustrate the construction and manufacture ofa hammer 20 embodying the present invention, and FIGS. 9-11 illustrate ahandleless mallet 22 likewise embodying the invention. Both strikingtools 20 and 22 include a lightweight hollow core 24 having a pair ofimpact heads 26 fitted over the ends of the core, and a molded outercladding or encasement 28 which ensheathes portions of the impact headsand the hollow core to bind them together. During formation of the outerencasement 28, the hollow core 24 is substantially filled andstructurally backstopped by a flowable filler material 30 to enable theotherwise lightweight core 24 to withstand injection molding pressureand temperature conditions.

The present invention permits use of a hollow core 24 constructed from aminimum mass of lightweight material, such as a molded or extrudedplastic tubular shell, wherein the hollow core may be constructed withinadequate structural strength and rigidity to withstand compressivepressures, etc., applied thereto in the course of injection moldingprocesses to form the outer encasement 28. More particularly, the hollowcore 24 defines a generally tubular or cylindrical thin-walled structurewith an open interior volume. During injection molding, this interiorvolume is substantially completely filled by the filler material 30,selected to provide a rigid structural backstop which reinforces andretains the shape integrity of the core 24. The filler material 30 isadapted for removal, in whole or in part, from the hollow core 24 of thestriking tool 20 or 22 subsequent to molded formation of the outerencasement 28, thereby providing a lightweight tool componentconstructed from a comparative minimum of constituent materials.

With reference to FIGS. 1-8, the hammer 20 is of the soft-face, deadblowvariety and includes, generally, a hammer head 32 and a handle 34 whichprovides a grip 36, and which extends from the hammer head at a neckportion 38. In this embodiment, the head 32 includes the lightweighthollow core 24 filled with the flowable filler material 30 andsupporting a pair of impact heads 26 on opposite ends. The moldedcladding or encasement 28 also forms the handle 34 during the moldingprocess. Some or all of the filler material 30 is removable from thehollow core 24 through an access port 40 subsequent to formation of theencasement 28. In one form, a portion of the filler material 30 remainswithin the head 32 to provide the hammer 20 with deadblow or nonrecoilcharacteristics. A reinforcing bar 42 is inserted into the handle 34 soas be disposed generally centrally therein and extending the lengththereof. The reinforcing bar 42, when so positioned, also closes theaccess port 40.

More particularly, as shown in FIG. 2 the hollow core member 24 isgenerally cylindrical and defines an interior chamber 44. An aperture 46is provided in the hollow core 24 which forms a portion of the accessport 40, and allows for the introduction of flowable filler material 30.

Prior to placing the filled core 24 within an injection mold 48, twoimpact heads 26 are fitted over the ends of the core. Each of the impactheads 26 include an impact face 50 and a skirt 52 which extends awayfrom the impact face. The skirt 52 and the impact face 50 cooperativelydefine an open-sided, generally cylindrical internal chamber into whichan end of the core 24 is snugly received. The skirt 52 is furtherprovided with a series of beads or rings 54 on the external surfacethereof, to facilitate securing the impact heads 26 to the hollow core24 by the molded plastic encasement 28 following the molding process(FIG. 7).

The assembled core 24 and impact heads 26 are placed within theinjection mold 48, as shown in FIG. 3. An elongate core pin 56 ispositioned with one end placed either over or within the aperture 46, toextend from the hollow core 24 as a skeletal member for the hammerhandle 34. As shown in FIG. 4, plastic encasement material is introducedinto the mold 48 under suitable injection molding conditions to form anintegral cladding which ensheathes the skirts 52 of the impact heads 26as well as an intermediate portion of the hollow core 24, and also formsthe hammer handle 34 about the core pin 56. The encasement material ispermitted to cure, thereby defining the plastic molded encasement 28.

The resultant hammer is separated from the mold 48, and the core pin 56is withdrawn from the molded plastic handle 34 to open the now formedaccess port 40, which includes an elongated channel 58 extendinggenerally centrally the length of the handle 34, and the aperture 46with which the channel 58 is aligned (FIG. 11). Some or all of thefiller material 30 can be drained from the hollow core 24 to provide alightweight hammer head 32. In a preferred form, a portion(approximately 2/3 to 3/4) of the filler material 30 is retained withinthe hammer head 32, and the access port 40 is plugged and sealed bymeans of a fiberglass shaft or reinforcing bar 42 which is press-fitinto the channel 58 (FIG. 6). In this regard, the fiberglass reinforcingbar 42 is provided with external surface irregularities 60 (FIG. 8) andis preferably heated prior to being driven into the channel 58. Theheated reinforcing bar 42 has a diameter slightly larger than thediameter of the channel 58 such that as it is driven into thethermoplastic encasement 28 defining the handle 34, the thermoplasticmaterial defining the channel 58 is softened and flows into intimatecontact around the surface irregularities 60 and then hardens as theheat of the reinforcing bar 42 is dissipated. This serves to securelyhold the reinforcing bar 42 in place within the channel 58.

The reinforcing bar 42 advantageously minimizes any warping orcold-flowing deformation of the handle 34 during use, and significantlystrengthens the handle so that the hammer 20 may be used effectively asa striking tool. The core pin 56 and the filler material 30 removed fromthe handle 34 and the hammer head 32 may be reused.

FIGS. 9-11 illustrate the manufacture of a mallet-like striking tool 22,which is identical in virtually every respect to the hammer 20 describedabove, with the exception that no handle 34 is provided. The samereference numbering system utilized in connection with the hammer 20will be utilized in the description of the mallet 22 for consistency ofidentification of similar tool components.

In this embodiment, the mallet 22 includes a lightweight core 24 filledwith the flowable filler material 30 and having a pair of impact heads26 fitted over the opposite ends thereof. When placed into the injectionmold 48, a plug 62 for the aperture 46 extends therefrom to create ashort channel 58 through the plastic molded encasement 28 following theinjection molding process. Again, the channel 58 and the aperture 46define the access port 40 through which some or all of the fillermaterial 30 can be drained from the hollow core 24 (FIG. 11). The mallet22 is, essentially, the hammer head 32 manufactured without the handle34 of the embodiment described above. The plastic molded encasement 28generally ensheathes the skirts 52 and the intermediate portion of thehollow core 24, while leaving the impact faces 50 exposed.

From the foregoing it will be appreciated that striking toolsmanufactured in accordance with the present invention utilizeinterchangeable components which may be selected to design a custom handtool for a specific working environment, which hand tool may be made ofthe most economical materials. In the striking tools 20 and 22illustrated, more expensive high strength materials are utilized onlywhere they will be needed. The impact heads may be selected from a widevariety of materials, for example nylon, polyurethane, and soft vinyls,that provide a wide range of working characteristics, from relativelyhard impact face surfaces to very soft. The use of adhesives or screw orrivet-type mechanical locking of the impact heads 26 to the hammer head32 has been eliminated to improve reliable manufacture of the strikingtools. The deadblow characteristics, if desired, can be closelyregulated by the amount of flowable filler material 30 retained withinthe hollow core 24 following the molding process. Moreover, thereinforcing bar 42 provides significant strength enhancement to thehandle 34.

The present invention further provides an improved method for makingplastic encased tool components having a lightweight hollow core,wherein the hollow core is structurally backstopped and reinforced bythe flowable filler material 30 during injection molding. Subsequent toinjection molding of the outer encasement 28, some or all of the fillermaterial 30 can be removed quickly and easily from the core to provide alightweight and relatively low cost tool component.

A variety of further modifications and improvements to the inventiondescribed herein will be apparent to those skilled in the art.Accordingly, no limitation on the invention is intended by way of theforegoing description and accompanying drawings, except as set forth inthe appended claims.

I claim:
 1. A method of making a striking tool, comprising the stepsof:filling an elongate hollow core member with a flowable fillermaterial; placing an impact head having an impact face and a skirtextending away from the face, adjacent to one end of the core membersuch that the skirt fits over said one end; molding an outer encasementabout the core member and the skirt so as to bind the impact head to thecore member, whereby the filler material provides a structural backstopto maintain the shape integrity of the core member during the moldingstep; and removing at least a portion of the filler material from thecore member subsequent to the molding step.
 2. The method of claim 1,wherein the filling step comprises filling the hollow core member withsmall rigid pellets.
 3. The method of claim 2, wherein the pellets havea diametric size on the order of 0.005 inch.
 4. The method of claim 1,including the step of closing an access port formed in the core member,subsequent to the filling step and prior to the molding step, andwherein the removing step includes re-opening the access port.
 5. Themethod of claim 1, wherein the molding step comprises an injectionmolding step to form a plastic outer encasement on the core member. 6.The method of claim 1, including the step of placing a second impacthead having a second impact face and a second skirt extending away fromthe second face, adjacent to a second end of the core member prior tothe molding step, and wherein the molding step results in binding bothimpact heads to the core member.
 7. The method of claim 1, including thestep of forming a handle for the striking tool during the molding step.8. The method of claim 7, including the step of inserting a reinforcingrod generally centrally into the handle so as to extend the lengththereof.
 9. The method of claim 8, including the steps of formingsurface irregularities on the reinforcing rod, and heating thereinforcing rod prior to inserting it into the handle.
 10. The method ofclaim 1, wherein the removing step comprises removing a limited portionof the filler material from the core member, and sealing the core memberto retain a residual portion of the filler material therein.
 11. Amethod of making a striking tool, comprising the steps of:forming a coremember defining a hollow interior space and an access port opening intothe interior space; filling the interior space of the core member with aflowable filler material; closing the access port to retain the fillermaterial within the interior space; placing an impact head having animpact face and a skirt extending away therefrom, adjacent to one end ofthe hollow core member such that said one end of the core member isdisposed within the skirt; placing the core member with filler materialtherein and the impact head thereon, into a mold cavity; injecting aplastic material into the mold cavity to form a resilient outerencasement on the core member and the skirt of the impact head, andallowing the plastic material to cure to form the striking tool;removing the striking tool from the mold cavity; and opening the accessport in the core member and removing at least a portion of the fillermaterial therefrom.
 12. The method of claim 11, wherein the fillermaterial comprises solid pellets having a diametric size on the order of0.005 inch.
 13. The method of claim 11, including the step of forming ahandle for the striking tool during the molding step.
 14. The method ofclaim 13, including the step of re-closing the access port after alimited portion of the filler material has been removed from the coremember to retain a residual portion of the filler material therein. 15.The method of claim 14, wherein the step of re-closing the access portincludes the step of inserting a reinforcing rod into the handle so asto be disposed generally centrally therein and extending the lengththereof.
 16. A method of claim 15, including the steps of formingsurface irregularities on the reinforcing rod, and heating thereinforcing rod prior to inserting it into the handle.
 17. The method ofclaim 15, including the step of placing a second impact head having asecond impact face and a second skirt extending away from the secondimpact face, adjacent to a second end of the core member prior to themolding step, and wherein the molding step results in binding bothimpact heads to the core member.